Blister films are particularly suited for the casting or molding of frangible products or dosage forms which contain certain types of pharmaceuticals. These products are commonly made using lyophilization or freeze-drying processes. Alternative techniques, such as solid state dissolution methods, are also used to produce dosage forms which are frangible as well. These processes typically involve depositing a liquid form of the product into the blister(s), and then subjecting the liquid-containing blister to various processes to form the final solid product while in the blister(s). The products remain in the blister until they are ready for use, at which time the packets are opened and the product removed therefrom.
One disadvantage associated with polymeric blister films is permeability, which creates potential storage difficulties in protecting the product from the surrounding atmosphere despite sealing efforts. Such concerns have led to the development of laminated blister films in which a metal foil is sandwiched between polymeric films on either side. These films are less permeable than purely polymeric films. However, some films become distorted when subjected to heat treatments which can generate irregularities in the molded or cast products and making subsequent handling of the blister pack more difficult. Although some laminated films that are more stable under heat treatment have been developed, such as those disclosed in European Patent Application Nos. EP 0 646 367 and 0 710 101 for example, such laminated films are not suitable for the heat-forming of blisters therein. The metal foil layer is typically made of aluminum and is well-suited for cold forming techniques.
Published International Patent Application No. WO 99/08857A1 discusses the difficulties associated with creating indicia on the base of blisters formed with laminated films containing both metal foils and polymeric layers wherein the indicia are created simultaneously with the formation of the blisters themselves.
There is a need for improved methods for preparing molded or cast products in blister packs bearing indicia, especially with blisters formed from laminated films and having indicia on the interior surface to likewise emboss the opposing surface of the cast product.